Japan's [Images] Kazuki Nakajima will race for Williams next season, the Formula One team confirmed on Wednesday.

The 22-year-old son of former grand prix racer Satoru Nakajima will partner Germany's [Images] Nico Rosberg, also 22 and the son of Finland's 1982 world champion Keke, at the Toyota-powered team.

Nakajima, who was the team's official test and reserve driver this year, raced for Williams in the season-ending Brazilian Grand Prix after Austrian Alexander Wurz announced his retirement.

Although he injured a mechanic in a pit lane incident at Interlagos, the youngster impressed with the fifth fastest race lap and a 10th place finish after starting 19th.

"This is the crowning of a great year for me," the Japanese said in a team statement.

"I am very grateful to Toyota for the support I have had through the Toyota driver's programme and to Williams for the team's faith in me.

"There is plenty of work to be done before next season starts but I am resolved to do whatever is necessary and to show Williams and Toyota that they have made a good investment."

Rosberg has been with Williams since his debut in 2006 but his future with the former champions has been uncertain, with the youngster considered the leading candidate to replace Fernando Alonso [Images] as Lewis Hamilton's [Images] team mate at McLaren.

Spain's double world champion split with the Mercedes-powered team last week after a breakdown in their relationship over a traumatic season.

Williams said, however, that the highly-rated German would remain "the mainstay of the team's continued drive towards the front of the field".

The Grove-based team finished last season fourth overall, their standing enhanced by McLaren being stripped of all their constructors' points for a spying controversy involving leaked Ferrari [Images] technical information.

"Nico will be racing for the team for his third consecutive year after demonstrating impressive and widely applauded form in 2007," team owner Frank Williams said.

"Nico will be ably partnered by Kazuki, who has impressed the team over the past year. He has pace and the right aptitude to develop into a competitive Formula One racer."

Nakajima senior spent five seasons in Formula One, making his race debut with Lotus Honda in 1987 and taking career best fourth places in the 1987 British Grand Prix and 1989 Australian Grand Prix.